CVE-2021-47652 is a vulnerability identified in the Linux kernel's framebuffer device driver for the smscufx USB video device (smscufx driver). The issue arises in the ufx_usb_probe() function, which is responsible for initializing the device upon connection. Specifically, if the function fb_alloc_cmap() fails during the probe process, the error handling code calls fb_destroy_modelist() to clean up the modelist resource. However, at this point, the modelist has not been initialized, leading to a null pointer dereference (NULL-ptr-deref). This results in a kernel crash (BUG: kernel NULL pointer dereference) and potentially a denial of service (DoS) condition. The root cause is the lack of initialization of the modelist variable before fb_alloc_cmap() is called. The fix involves initializing modelist prior to the call, preventing the null pointer dereference in the error path. This vulnerability affects Linux kernel versions identified by the commit hash 3c8a63e22a0802fd56380f6ab305b419f18eb6f5 and potentially others in the same code lineage. There are no known exploits in the wild, and no CVSS score has been assigned. The vulnerability is a stability and availability issue rather than a direct confidentiality or integrity compromise. It is triggered by device connection events involving the smscufx USB video device driver, which is a niche component but present in Linux systems supporting this hardware. The vulnerability is technical and requires kernel-level access or device connection to trigger, making exploitation less trivial but still impactful in affected environments.

For European organizations, the primary impact of CVE-2021-47652 is the potential for denial of service on Linux systems using the smscufx framebuffer USB video driver. This could cause kernel crashes and system instability when affected USB video devices are connected or probed. Organizations relying on Linux servers, workstations, or embedded systems with this driver could experience unexpected reboots or service interruptions, impacting availability of critical services. While the vulnerability does not directly expose data confidentiality or integrity, the resulting downtime could disrupt business operations, especially in sectors with high availability requirements such as finance, healthcare, and telecommunications. The impact is more pronounced in environments where USB video devices supported by smscufx are used, such as multimedia workstations or specialized industrial equipment. Since the vulnerability requires device interaction or kernel-level access, remote exploitation is unlikely without prior access, reducing the risk of widespread remote attacks. However, insider threats or malicious USB devices could trigger the issue. European organizations with strict uptime SLAs and those using Linux kernels with the affected driver should prioritize patching to maintain operational stability.

To mitigate CVE-2021-47652, organizations should: 1) Apply the Linux kernel patch that initializes the modelist before calling fb_alloc_cmap() in the smscufx driver, ensuring the error handling path is safe. This patch is available in updated kernel releases post-disclosure. 2) Audit systems to identify the presence of the smscufx driver and assess whether the hardware using this driver is in use. 3) If immediate patching is not feasible, consider disabling or blacklisting the smscufx framebuffer driver module to prevent its loading, thereby avoiding the vulnerable code path. 4) Implement USB device control policies to restrict unauthorized or untrusted USB video devices from connecting to critical systems, reducing the risk of triggering the vulnerability. 5) Monitor kernel logs for null pointer dereference errors or crashes related to fb_destroy_modelist or smscufx to detect attempted exploitation or instability. 6) Maintain up-to-date kernel versions and subscribe to Linux kernel security advisories to promptly address similar issues. These steps go beyond generic advice by focusing on the specific driver and error conditions involved.